Study of ion field desorption for compact piezoelectric ion accelerators

Studies are being conducted to create a compact neutron source to be used for active interrogation in areas where a large facility is impractical [1]. Using structures with nanometer scale radii of curvature, a large electric field can be created which will produce deuterium ions through field desorption and ionization in a portable system [2]. Neutron production is directly related to the ion current [3], making emission arrays promising. Field ion desorption structures are being designed as ion emitting anodes for use in deuterium deuterium neutron generators based on piezoelectric transformers. Ions are accelerated by a piezoelectric high voltage generator, composed of a rotated y-cut bar of lithium niobate. When driven with an electric signal near the acoustic resonant frequency of the device, a high voltage is created on the surface of the piezoelectric crystal. The end goal is to attach a field desorption structure to an electrode on a piezoelectric crystal for subsequent ion acceleration. Two methods of ion generation were considered. The first uses the high electric field generated in the region of a field enhanced structure to ionize a low pressure background gas of deuterium. The second method uses a deuterated tip, where the high electric field near a field enhancement directly produces deuterium ions. In both cases the ions are then accelerated by the high voltage from the accelerator into a deuterated target. Possible methods for ion field desorption source fabrication have been developed. The design of the structures and the estimated ion current is presented.